Belt termination and tensioning in a pulley arrangement for a robotic arm

ABSTRACT

In one variation, a pulley arrangement includes a base pulley portion rotatable within a driving plane, an adjustable pulley portion coupled to the base pulley portion wherein the adjustable pulley portion is rotatable relative to the base pulley portion within the driving plane, and a driving member including an end coupled to the adjustable pulley portion wherein at least a portion of the driving member is wrapped at least partially around the adjustable pulley portion. In another variation, a pulley arrangement includes a base pulley portion rotatable around an axis, an adjustable pulley portion coupled to the base pulley portion and movable in a first direction parallel to the axis, and a sliding block engaged with the adjustable pulley portion, wherein the sliding block moves in a second direction different from the first direction, in response to compression of the adjustable pulley portion against the base pulley portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application Ser. No.62/395,704, filed on Sep. 16, 2016, which is hereby incorporated by thisreference in its entirety.

TECHNICAL FIELD

This invention relates generally to the field of robotic arms, and morespecifically to pulley arrangements for a robotic arm.

BACKGROUND

Robotic arms are used in a variety of applications, such as inmanufacturing and surgical procedures. For example, robotic-assistedminimally-invasive surgery (MIS) involves techniques intended to reducetissue damage during a surgical procedure. Robotic-assisted laparoscopicprocedures, for example, typically involve creating a number of smallincisions in the patient (e.g., in the abdomen), and introducing one ormore instruments (e.g., one or more tools, at least one camera, etc.)through the incisions into the patient. The surgical procedures are thenperformed by using the introduced tools controlled by one or morerobotic arm assemblies commanded by an operator, with the visualizationaid provided by the camera. Generally, MIS provides multiple benefits,such as reduced patient scarring, less patient pain, shorter patientrecovery periods, and lower medical treatment costs associated withpatient recovery.

In some variations, at least a portion of a robotic arm may be drivenwith one or more pulley arrangements (e.g., a pulley transmission, suchas one including pulleys and cables that are wrapped around thepulleys). However, one drawback of pulley arrangements is that they tendto fail and/or lose performance due to cable loosening and/or cablebreakage over the course of use. Furthermore, in some applications, itmay be desired that pulley arrangements in a robotic arm are relativelycompact, yet able to withstand high driving forces.

SUMMARY

In some variations, a pulley arrangement (e.g., a pulley transmission orother suitable pulley arrangement) may include a base pulley portionrotatable within a driving plane, an adjustable pulley portion coupledto the base pulley portion and rotatable relative to the base pulleyportion within the driving plane, and a driving member including a firstend coupled to the adjustable pulley portion, wherein at least a portionof the driving member is wrapped at least partially around theadjustable pulley portion. In some variations, the adjustable pulleyportion may include a member that is coaxial with the base pulleyportion. The adjustable pulley portion may be lockable in a selectedrotational position relative to the base pulley portion, such that, forexample, the pulley arrangement sets a selected level of tension in thedriving member.

The adjustable pulley portion may, for example, be coupled to the basepulley portion via at least one opening in at least one of theadjustable pulley portion and the base pulley portion. In somevariations, for example, the pulley arrangement may include at least onefastener passing through the at least one opening such that the fastenermay be lockable in the at least one opening to thereby lock a rotationalposition of the adjustable pulley portion relative to the base pulleyportion. For example, the at least one opening may be a slot, and thefastener may be lockable in a selected location within the slot tothereby lock a rotational position of the adjustable pulley portionrelative to the base pulley portion. As another example, the at leastone opening may be one of a plurality of openings in at least one of theadjustable pulley portion and the base pulley portion. Each opening maycorrespond to a respective rotational position of the adjustable pulleyportion relative to the base pulley portion. The fastener may belockable in a selected opening of the plurality of openings to therebylock a rotational position of the adjustable pulley portion relative tothe base pulley portion.

In some variations, the pulley arrangement may include a movable elementengaged with the adjustable pulley portion, where the movable element isadjustable to thereby rotate the adjustable pulley portion relative tothe base pulley portion. For example, the movable element may include athreaded member (e.g., fastener, threaded rod, etc.) with one end (e.g.,including a hemi-spherical head or other suitable contact shape) thatcontacts the adjustable pulley portion. As the movable element'sposition is adjusted, the movable element may cause the adjustablepulley portion to move relative to the base pulley portion.

The pulley arrangement may, in some variations, include at least asecond pulley, where the driving member wraps at least partially aroundthe second pulley. The second pulley may, for example, be placed at asuitable distance from the base pulley portion. A second end of thedriving member may be coupled to the second pulley. Additionally oralternatively, a second driving member may include an end coupled to thebase pulley portion and another end coupled to the second pulley.

Generally, in some variations, a pulley arrangement may include a basepulley portion rotatable around an axis, an adjustable pulley portioncoupled to the base pulley portion and movable in a first directionparallel to the axis; and a first sliding block engaged with theadjustable pulley portion. The first sliding block may be configured tomove in a second direction different from the first direction, inresponse to compression of the adjustable pulley portion against thebase pulley portion. The pulley arrangement may, in some variations,further include a driving member having a first end that is coupled tothe first sliding block, and at least a portion of the driving membermay be wrapped at least partially around the first sliding block and/oraround the adjustable pulley portion. In some variations, the pulleyarrangement may include one or more additional pulleys, such as an idlerpulley, where at least one driving member wraps at least partiallyaround the idler pulley.

The adjustable pulley portion and/or the first sliding block may includeat least one sloped surface. For example, the sloped surface may includea helical surface. A sloped surface of the adjustable pulley portionmay, for example, engage with the sliding block. Additionally oralternatively, a sloped surface of the sliding block may engage with theadjustable pulley portion.

In some variations, the pulley arrangement may include a second slidingblock engaged with the adjustable pulley portion. A second end of thedriving member, or an end of a second driving member, may be coupled tothe second sliding block. The first and second sliding blocks may beconfigured to move circumferentially toward each other in response tocompression of the adjustable pulley portion against the base pulleyportion. Their movement may be at about equal rates in response to suchcompression (e.g., to provide bilaterally symmetrical tensioning) ordifferent rates. In some variations, the first and second sliding blocksmay be disposed in an arcuate gap defined at least in part by theadjustable pulley portion. In some variations, the first and/or secondsliding blocks may be configured to move in an arcuate path, a linearpath, or other suitable path in response to compression of theadjustable pulley portion against the base pulley portion.

The adjustable pulley portion may include a single member or multiplemembers engaged with one or more sliding blocks. For example, theadjustable pulley portion may include a first member engaged with thefirst sliding block and a second member engaged with the second slidingblock, such that the first and second members are movable parallel tothe axis around which the base pulley portion rotates. The axialposition of the adjustable pulley portion relative to the base pulleyportion may be lockable (e.g., with one or more fasteners, such as oneor more fasteners coupling the adjustable pulley portion and the basepulley portion). In some variations, the adjustable pulley portion maybe adjacent the base pulley portion, such as axially aligned. In somevariations, the adjustable pulley may be disposed in a recess of thebase pulley portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are illustrative schematics of an exemplary variation ofa robotic arm, and an exemplary variation of a pitch assembly in arobotic arm, respectively. FIGS. 1C and 1D are perspective detailedviews of an exemplary variation of a pitch assembly with a pulleyarrangement.

FIG. 2A is an illustrative schematic of an exemplary variation of amulti-layered driving member in a pulley arrangement. FIG. 2B is adetailed view of a shear substrate in an exemplary variation of adriving member.

FIGS. 3A and 3B are a perspective view and exploded views, respectively,of an exemplary variation of a driving member attachment to a pulley.

FIGS. 4A-4D are perspective, cross-sectional, side, and perspectivedetailed views, respectively, of an exemplary variation of a drivingmember attachment to a pulley.

FIGS. 5A and 5B are perspective and side views, respectively, of anexemplary variation of a driving member attachment to a pulley.

FIGS. 6A-6D are perspective, cross-sectional, side, and detailed views,respectively, of an exemplary variation of a driving member attachmentto a pulley.

FIG. 7 is a side view of an exemplary variation of a driving memberattachment to a pulley.

FIG. 8 is a side view of an exemplary variation of a driving memberattachment to a pulley.

FIG. 9 is a side view of an exemplary variation of a driving memberattachment to a pulley.

FIG. 10A is an exploded view of an exemplary variation of a drivingmember attachment to a pulley. FIGS. 10B-10D are schematic illustrationsof a method for assembling the driving member attachment depicted inFIG. 10A.

FIG. 11 is a schematic illustration of an exemplary variation of abrazed driving member attachment to a pulley.

FIG. 12A is a perspective view of an exemplary variation of a pulleyarrangement enabling tensioning of a driving member. FIGS. 12B and 12Care a sectional perspective view and a side view, respectively, of anadjusting pulley for adjusting tension in the pulley arrangementdepicted in FIG. 12A.

FIGS. 13A-13C are schematic illustrations of a method of adjustingtension in a driving member with the adjusting pulley depicted in FIG.12A.

FIG. 14A is a side view of an exemplary variation of a pulleyarrangement enabling tensioning of a driving member. FIG. 14B is a sideview of an adjusting pulley in the pulley arrangement depicted in FIG.14A.

FIGS. 15A and 15B are perspective and top views, respectively, of anexemplary variation of a pitch link assembly incorporating one or morepulley arrangements.

FIG. 16A is a perspective view of an exemplary variation of a pulleyarrangement enabling tensioning of a driving member. FIG. 16B is a sideview with detailed inset views of an adjusting pulley and an idlerpulley in the exemplary variation of a pulley arrangement depicted inFIG. 16A. FIG. 16C is an exploded view of an exemplary adjusting pulley.FIG. 16D is an exploded view of an exemplary idler pulley. FIGS. 16E and16F are perspective views of an exemplary adjusting pulley. FIG. 16G-16Iare perspective views of a sliding block, an adjustable pulley portion,and a base pulley portion, respectively, of an exemplary adjustingpulley.

FIG. 17 is a perspective view of an exemplary variation of a pulleyarrangement enabling tensioning of a driving member.

FIGS. 18A and 18B are side and perspective views, respectively, of anexemplary variation of a pulley arrangement enabling tensioning of adriving member.

DETAILED DESCRIPTION

Examples of various aspects and variations of the invention aredescribed herein and illustrated in the accompanying drawings. Thefollowing description is not intended to limit the invention to theseembodiments, but rather to enable a person skilled in the art to makeand use this invention.

Robotic Arm Overview

Generally, a robotic or robotic-assisted surgical system (e.g., toenable a minimally-invasive surgical procedure) may include one or morerobotic arms for manipulating surgical tools, such as duringminimally-invasive surgery. As shown in FIG. 1A, a robotic arm 100 mayinclude a plurality of links (e.g., 112 a, 112 b, 112 c, 112 d, etc.),and a plurality of actuated joints that enable relative movement betweenadjacent links. Additionally, a tool driver 130 may be coupled to adistal end of the robotic arm 100 and be configured to hold and actuatea surgical instrument 140 passing through a cannula 150. During use ofthe robotic arm 100 for a surgical procedure, a proximal end of therobotic arm 100 may be mounted or otherwise coupled to a structure(e.g., a surgical table, cart, wall, ceiling, etc.) at a mounting pointnear the patient during a surgical procedure. The surgical instrument140 may pass through the cannula 150 through an incision or other entrypoint in the patient. Generally, the robotic arm 100 and/or tool driver130 may be manipulated by a user in order to control the surgicalinstrument 140 within the patient (e.g., to perform surgical tasks, toposition a camera, etc.). Other examples of a robotic surgical systemare described in U.S. Patent Application Ser. No. ______ filedconcurrently herewith and titled “ROBOTIC ARMS” with attorney docket no.VESU-004/01US 326240-2095, which is hereby incorporated in its entiretyby this reference.

As shown in FIGS. 1A and 1B, the robotic arm 100 may further include apitch assembly 120. The pitch assembly may include a first end 126coupled to a portion of the robotic arm, and a distal end 128 which iscoupled to the tool driver 130. As shown in FIG. 1B, the pitch assembly120 may include at least a first pitch link 122 and a second pitch link124 that actuate the cannula in a particular direction P around aparticular axis, referred to herein as a pitch axis (e.g., pictured inFIG. 1B as passing through the page and coincident with, ornear-coincident with, a mechanical remote center of motion, or RCM). Forexample, the first pitch link 122, the second pitch link 124, and thetool driver 130 may move as three links of a four-bar linkage (e.g.,generally a parallelogram) that includes “ground” as a fourth link,constrained with a drive mechanism (such as a pulley arrangement orother suitable pulley transmission), in order to move the cannula aroundthe pitch axis in a pitch direction P. Through this four-bar linkagemotion, the pitch assembly 120 may replicate rotation of the first pitchlink 122 around Axis A (pictured in FIGS. 1C and 1D) into rotation ofthe cannula around the pitch axis (e.g., around the mechanical RCM),where Axis A and the pitch axis are generally offset and parallel. Insome variations, the pitch assembly may include any suitable number oflinks “n” to form an n-bar linkage. Accordingly, actuation of the firstpitch link 122 around its first end 126 at Axis A may control a pitchmovement of the cannula in the direction P. Although the pitch assembly120 is primarily described herein as actuating the cannula around apitch axis, it should be understood that in other variations or otherorientations of the pitchy assembly 120, the links 122 and 124 may beconfigured to actuating the cannula around a particular axis in anotherdirection (e.g., a yaw axis), depending on, for example, how theassembly 120 is oriented, etc.

The pitch assembly 120 may be configured to operate the surgicalinstrument 140 about the RCM with increased ease, speed, andflexibility. Additionally, the pitch assembly 120 may be configured tocollapse into a compact pose or configuration. For example, as shown inFIGS. 1C and 1D, the first pitch link 122 may be shorter than the secondpitch link 124, such that the first pitch link 122 may rotate relativeto the second pitch link 124 without physical interference and allow thepitch assembly 120 to collapse or fold down against itself. Such aconfiguration can, for example, be useful for storage, transport, and/orincreased range of motion of the robotic arm 100, such as during asurgical procedure.

The pitch linkage assembly 120 may include a series of pulleys and aseries of driving members (e.g., metal bands, cables, chains, othersuitable driving members, etc.) connecting the pulleys that facilitatefour-bar linkage movement. For example, with reference to FIGS. 1C and1D, the first pitch link 122 may be coupled to an actuator (not shown)that drives rotation of first pitch link 122 around Axis A, while thesecond pitch link 124 may be rotationally coupled to the tool driver.The first pitch link 122 may include a first pulley 162 coupled to theactuator and located generally at a proximal point of first pitch link122, within an internal space of first pitch link 122. The first pitchlink 122 may also include a second pulley 164 located generally at adistal point of the first pitch link 122, within the internal space ofthe first pitch link 122. The second pulley 164 may be rigidly fixed toa proximal point of the second pitch link 124.

Additionally, the second pitch link 124 may include a third pulley 166located generally at a proximal point of the second pitch link 124,mounted on and rigidly fixed to a shaft of the first pitch link 122 thatextends into an internal volume of the second pitch link 124, such thatwhen the first pitch link 122 rotates, the third pulley 166 rotatescorrespondingly. The second pitch link 124 may also include a fourthpulley 168 located generally at a distal point of the second pitch link124, within the internal space of the second pitch link 124. The tooldriver may be rotationally coupled to the distal point of the secondpitch link 124 and thus constrained to move when the fourth pulley 168rotates around Axis A′.

At least one driving member (not shown) may wrap around the first andsecond pulleys 162 and 164 such that when an actuator drives rotation ofthe first pitch link 122 at its first end 126 around Axis A, theorientation of the second pitch link 124 remains fixed relative to theorientation of the housing of the actuator. Similarly, at least onedriving member (not shown) may wrap around the third and fourth pulleys166 and 168 such that when the second pitch link 124 rotates, the tooldriver orientation remains fixed relative to the orientation of thefirst pitch link 122. In sum, rotation of the first pitch link 122around Axis A may be transformed through the system of pitch links,pulleys, and bands into rotation of the tool driver around Axis A′ viafour-bar linkage movement (e.g., in a parallelogram), and thus drivesmovement of the cannula around the pitch axis as described above (e.g.,around a mechanical RCM). In some variations, the at least one drivingmember may include one or more cables, belts, and/or other suitabledriving members or driving members.

For example, in the variation shown in FIGS. 15A and 15B, the pitchassembly 1556 includes a first pitch link 1556 a, a second pitch link1556 b, and a set of pulleys and driving members (e.g., bands)configured to constrain motion of the pitch assembly in a manner similarto the variation described above with reference to FIGS. 1C and 1D. Inthis variation, the first pitch link 1556 a has a terminating pulley1510 configured to couple to the housing of a joint module actuator orother chassis of the robotic arm, and the first pitch link 1556 a isrigidly fixed to an adjustable pulley 1514 located within the secondpitch link 1556 b. The second pitch link 1556 b is rigidly fixed to anadjustable pulley 1512 and further includes a terminating pulley 1516configured to couple to a tool driver. Rotational movement of thevarious components may be facilitated by bearings, such as a bearing1530 a facilitating relative movement of the rest of the robotic arm andthe first pitch link 1530 a, a bearing 1530 b facilitating relativemovement between the first and second pitch links 1556 a and 1556 b, anda bearing 1530 c facilitating relative movement of the second pitch link1556 b and the tool driver.

A pair of driving members (e.g., belts or bands) 1520 a and 1520 b mayextend between terminating pulley 1510 and adjustable pulley 1512, withfirst ends terminating rigidly at the terminating pulley 1510 (e.g.,coupled by welding or other suitable connection) and second ends coupledto the adjustable pulley 1512 (e.g., through welding or other suitableconnection). Similarly, a pair of driving members (e.g., belts) 1522 aand 1522 b extend between terminating pulley 1516 and adjustable pulley1514, with first ends terminating rigidly at the terminating pulley 1516and second ends coupled to the adjustable pulley 1514. As a result ofthe driving member and pulley system, when the first pitch link 1556 ais rotated around terminating pulley 1510, the second pitch link 1556 btranslates in-plane without rotating (e.g., staying parallel to itsprevious orientation), while the terminating pulley 1516 moves in an arcabout the remote center of motion.

In some variations, a pulley arrangement (e.g., pulley transmission orother suitable pulley arrangement) in a robotic arm (e.g., a pitchassembly) may include one or more attachment configurations for couplinga driving member to a pulley with increased resistance against shearforces that otherwise may tend to decouple the driving member from thepulley, cause any multiple layers of a driving member (e.g., a stack oflayers, as described in further detail below) to slip relative to oneanother, and/or cause loss of tension in the driving member, and in amanner that occupies less overall volume and/or occupies less surfacearea of the pulley. Additionally or alternatively, the pulleyarrangement may include one or more tensioning mechanisms for adjustingtension in the driving member. For example, the driving member may betensioned to a predetermined tension during manufacturing, assembly,and/or calibration of the pitch assembly, to help guard against and/orcompensate for fatigue loads that otherwise may tend to cause thedriving member to slacken and result in poorer operational performancein the pulley arrangement. Various examples of attachment configurationsand tensioning mechanisms are described in further detail below.

Driving Member and Attachment

Generally, when a pulley arrangement is used, significant driving forcesmay be applied to the one or more driving members that wrap at leastpartially around a pulley and/or at the attachment point of the drivingmember to the pulley. For example, as the pulley arrangement is operated(e.g., at least one pulley rotates), one or more driving members may beloaded in tension. As another example, as the pulley arrangement isoperated, one or more attachment points for a driving member (where aterminating end of the driving member is coupled to a pulley) may loadedwith a shear force (e.g., relating to tensile load in the drivingmember). If such forces are significant enough, they may cause thepulley arrangement to fail in one or more different ways. For example,the driving member may break if driving forces exceed its tensilestrength, or an attachment point may fail if shear forces exceed theshear strength of the joint between the terminating end of the drivingmember and the pulley. In some variations, a driving member may bewrapped more than once around the entire circumference of the pulley,which may help shield the attachment point from experiencing the fullload of forces during operation of the pulley arrangement. However, evenin these variations the driving member and its attachment point to thepulley are still subject to failure due to the driving forces in thepulley arrangement, and the increased bulk of the pulley arrangement dueto extra wrapping may be undesirable in some applications.

Furthermore, in some applications, it may be advantageous to attach adriving member to a pulley using as little surface area of the pulley aspossible, in order to increase the amount of useful angular travel ofthe pulley (e.g., less “dead” wrap or “static” wrap of the drivingmember) and thus enable the pulley arrangement (and, for example, alinkage assembly driven by the pulley arrangement) to have a greaterrange of motion.

Below are exemplary variations of driving members, and exemplaryvariations of pulley-driving member attachment arrangements that may besecure, compact, and/or occupy less surface area of the pulley withoutsacrificing attachment strength of the driving member to the pulley. Itshould be understand that although at least some of the systems andmethods for attachment are primarily described herein as coupling twoends of one driving member to a pulley, the same systems and methods forattachment may be used to secure ends of two separate driving members toa pulley (i.e., one end of a first driving member and one end of asecond driving member to the pulley).

Driving Members

As shown in FIG. 2A, in some variations, a driving member 200 for apulley arrangement may include a plurality of layers of one or morematerials arranged in a stack, such that a load (e.g., tensile drivingforce) applied to the driving member is distributed across the multiplelayers. Generally, with multiple layers of materials load-sharing insuch a manner, the driving member as a whole may withstand a greaterapplied load before failing (e.g., due to cyclic loading around thepulley, and/or other factors). The layers of the driving member may bejoined at least a termination end of the driving member. Additionally oralternatively, layers of the driving member may joined along the length,or part of the length, of the driving member in lamination.

In some variations, as shown in FIG. 2A, at least some of the layers ofthe driving member may include a first material 210 and a secondmaterial 220 that interleaves with the primary material. The firstmaterial 210 may function to bear tensile loads applied to the drivingmember and may include, for example, metal, plastic, carbon fiber, etc.The second material 220 may function as a shear substrate that increasesshear strength at an attachment point. The second material 220 mayinclude, for example, an adhesive solution (e.g., a cyanoacrylateadhesive or other suitable liquid adhesive, a double-sided structuraladhesive, or suitable epoxy, etc.). As another example, as shown in FIG.2B, the second material 220 may additionally or alternatively includeparticles 222 (e.g., diamond particles, silicon carbide particles, etc.)suitable for deforming the lamination of the first material 210, suchthat they provide a physical connection between layers of the firstmaterial 210. The particles 222 may be mixed among a carrier solution ofadhesive and/or non-adhesive materials, and the particles may bedistributed and at least partially embedded into the adjoining surfacesof the first material 210 such that the particles are mechanicallylocked into the first material 210. In some variations, the particles222 may generally have a diameter that is up to about half the thicknessof the adjacent layer(s) of the first material 210. For example, in onevariation, if a layer of first material 210 includes a band about 0.002inches thick, the particles 222 may be up to about 25 microns indiameter. Such a physical connection transfers mechanical forces betweenthe layers of the first material 210 in response to applied shearforces, thereby increasing the overall stiffness of the joint. Variousother suitable mixtures of adhesive and/or non-adhesive solutions may bemixed with particles and cured prior to or during lamination of thefirst material 210. Additionally or alternatively, the second material220 may include a suitable filler material (e.g., aluminum-silicon,copper or copper alloy, nickel alloy, etc.) for brazing layers of thefirst material 210 together.

Dimensions and material choice for a multi-layered driving member may beselected depending on the needs for the specific application. Forexample, the thickness of a multi-layered driving member may depend onvarious factors such as the anticipated loads that the driving member isexpected to withstand, the type or types of materials in each layer, theradius of the pulley, the thickness of each layer, the number of layers,and the width of the driving member. As one example, generally, totalthickness of the driving member in a pulley arrangement for a roboticarm may range between about 0.2 millimeters and about 1 millimeter,between about 0.4 millimeters and about 0.8 millimeters, or betweenabout 0.50 millimeters and about 0.7 millimeters.

In one exemplary variation, a multi-layered driving member may includeabout six layers of metal (e.g., 301-HY stainless steel), where eachmetal layer may be about 0.05 millimeters thick. The metal layers, at atermination end of the driving member, may be interleaved with a mixtureof cyanoacrylate adhesive and diamond particles. The diamond particlesmay have a diameter of about 0.5 microns or 0.6 microns.

In other variations, the driving member may include any suitable numberof layers (e.g., at least two, three, four, five or more layers).Furthermore, although exemplary multi-layered driving members aredescribed above, the variations of attachment methods described belowmay be used in combination with any suitable kind of driving member(e.g., single layer of a belt or band) made of any suitable kind ofmaterial.

Compressive Attachment

In some variations, a terminating end of a driving member may beattached to a pulley in the pulley arrangement via at least acompressive arrangement. A compressive arrangement may provide goodresistance against fatigue over repeated operation of the pulleyarrangement, such that the driving member is less likely to loosen overtime. Additionally, a compressive arrangement may avoid weaknesses thatmay be introduced in the driving member material by other attachmentmethods using welding, which may cause undesirable heat stresses nearthe attachment point of the driving member to the pulley. Furthermore,when used in combination with fasteners or pins passing through holes inthe driving member, a compressive arrangement may exert a compressiveforce that provides good frictional contact to transfer loads, therebyreducing or eliminating stress concentration around the holes in thedriving member that would otherwise contribute to failure of the drivingmember around the attachment point.

Generally, a compressive arrangement for attaching a driving member to apulley may include compressing at least a portion of the driving member(e.g., a terminating end thereof) against the pulley. For example, atleast a portion of the driving member and the pulley may be sandwichedbetween two opposing surfaces. The opposing surfaces may, for example,be aligned and/or compressed toward each other with a fastener such as athreaded member (e.g., bolt or screw). Such a fastener may be securedwith a nut (e.g., locknut, jam nut, etc.). As further illustrated by theexamples described below, at least one of the opposing surfaces mayinclude, for example, an additional compressive component such as awasher or clamp plate that increases surface area and friction againstthe pulley and/or driving member, and thus increases shear strength ofthe attachment joint when the compressive arrangement is tightened andsecured with the fastener. As another example, at least a portion of thedriving member and the pulley may be compressed against the pulley witha wedge or other suitable compressive element. Other variations ofcompressive arrangements for attaching a driving member to a pulley orother surface are described herein.

In one exemplary variation, as shown in FIGS. 3A and 3B, a compressivearrangement 300 for coupling a driving member to a pulley may include apulley 310, a driving member 320, and a clamp 330. A suitable shearsubstrate (e.g., as described above with reference to FIG. 2B) such as acyanoacrylate adhesive may be disposed between the pulley 310 and thedriving member 320 and/or between the driving member 320 and the clamp330. The shear substrate between the pulley 310 and the driving member320 may be different or substantially similar to the shear substratebetween the driving member 320 and the clamp 330. As shown in FIG. 3A,at least one fastener 340 (e.g., threaded screw) may pass through a hole332 in the clamp, a hole 322 in the driving member, and a hole 312 inthe pulley.

The clamp 330 may include a plate with holes 332 formed therein (e.g.,by machining, 3D printing, casting, etc.). Although the clamp 330 isshown in FIGS. 3A and 3B as a generally flat or level plate with twoholes 332, it should be understood that in other variations, the clamp330 may be arcuate (e.g., arcuate with a similar radius of curvature asthe pulley 310) and include any suitable number holes, such as two,three, four, five, six, or more holes in any suitable pattern toaccommodate any suitable number of fasteners 340. At least some of theholes 332 may, in some variations, be countersunk for receiving theheads of the fasteners 340 such that the fasteners 340 lie generallyflush with the surface of the clamp 330. The clamp 330 may include amaterial that is softer than the material of the driving member so asnot to deform the driving member when the clamp 330 is tightened ontothe driving member. The clamp may, in some variations, have a thicknessgenerally the same as the thickness of the driving member, but mayalternatively have any suitable thickness. In some variations, thecircumferential length of the clamp 330 relative to the width of thedriving member may be between about 1:1.5 and about 1:3, or about 1:2.

In some variations, the one or more holes 312 in the pulley 310 may bethreaded to receive a threaded fastener 340 such that one or morefasteners 340 may sandwich and compress the clamp 330 and the drivingmember 320 against the pulley 310 in a compressive arrangement, as thefasteners 340 are advanced into the holes 312. Additionally oralternatively, a nut 342 (e.g., jam nut, lock nut, etc.) may engage witha distal end of a fastener 340 to secure the clamped assembly together.A threadlocker adhesive (e.g., LOCTITE) may, in some variations, beapplied to the threads of the fastener 340 to further secure the clampedassembly against fatigue and loosening.

As shown in FIG. 3A, the compressive arrangement 300 may include aplurality of fasteners 340 (e.g., at least two, three, four, five, etc.)to secure the compressive arrangement of the clamp 330, driving member320, and pulley 310. A desired particular arrangement of fasteners(size, number, etc.) for attaching the driving member 320 to the pulleywithout a weld may be assessed based on the geometry and/or materialproperties of the driving member and fasteners, and their effect onstress experienced at the interface between the driving member andfasteners.

For example, the mathematical expressions below may be used to determinedesired fastener diameter based at least in part on characterizations ofshear stresses of the driving member and fasteners, and on knowngeometries illustrated in FIG. 3B and other known material properties.Shear stress σ_(F) of the fasteners in the compressive arrangement maybe expressed as shown in Equation (1) below:

$\begin{matrix}{\sigma_{F} = {\frac{P_{F}}{A_{F}} = \frac{P_{F}}{N_{F}{\pi \left( \frac{D_{F}}{2} \right)}^{2}}}} & (1)\end{matrix}$

where P_(F)=force at the shear location of the fasteners, A_(F)=area ofthe fasteners at the shear location, N_(F)=number of fasteners,D_(F)=diameter of each fastener, and σ_(F)=ultimate tensile strength(UTS) of the fastener material.

Additionally, shear stress σ_(D) of the driving member may be expressedat shown in Equation (2) below:

$\begin{matrix}{\sigma_{D} = {\frac{P_{D}}{A_{D}} = \frac{P_{D}}{N_{D}{Y_{D}\left( {X_{D} - {N_{F}D_{F}}} \right)}}}} & (2)\end{matrix}$

where P_(D)=force at the shear location of the driving member,A_(D)=area of the driving member at the shear location, N_(D)=number oflayers in the driving member at the shear location, Y_(D)=thickness ofeach layer in the driving member, X_(D)=width of each layer in thedriving member, N_(F)=number of fasteners, D_(F)=diameter of eachfastener, and σ_(D)=ultimate tensile strength (UTS) of the drivingmember layer material.

Assuming that, at the interface between the driving member andfasteners, shear force P_(F) acting on the fasteners by the drivingmember is equal to the shear force P_(D) acting on the driving member bythe fasteners, Equations (3)-(6) can be developed:

$\begin{matrix}{P_{F} = P_{D}} & (3) \\{{\sigma_{F}A_{F}} = {\sigma_{D}A_{D}}} & (4) \\{{\sigma_{F}N_{F}{\pi \left( \frac{D_{F}}{2} \right)}^{2}} = {\sigma_{D}N_{D}{Y_{D}\left( {X_{D} - {N_{F}D_{F}}} \right)}}} & (5) \\{{{\frac{\sigma_{F}N_{F}\pi}{4}D_{F}^{2}} + {\sigma_{D}N_{D}Y_{D}N_{F}D_{F}} - {\sigma_{D}N_{D}Y_{D}X_{D}}} = 0} & (6)\end{matrix}$

Using Equation (6), the desired diameter D_(F) of each fastener can bedetermined using the quadratic formula

$\begin{matrix}{D_{F} = \frac{{- b} \pm \sqrt{b^{2} - {4{ac}}}}{2a}} & (7) \\{where} & \; \\{a = \frac{\sigma_{F}N_{F}\pi}{4}} & (8) \\{b = {\sigma_{D}N_{D}Y_{D}N_{F}}} & (9) \\{c = {\sigma_{D}N_{D}Y_{D}X_{D}}} & (10)\end{matrix}$

Equations (7)-(10) provide for one positive value and one negativevalue, with the positive value being the desired fastener diameter basedon the known or predetermined geometries and material characteristics ofthe driving member and fasteners.

In other words, once materials and particular geometries of thecompressive arrangement are selected and known, Equations (1)-(10) maybe applied to determine a desired fastener diameter for the compressivearrangement. Furthermore, in some variations, the compressivearrangement may include fastener sizes that incorporate additionalsafety factors (e.g., 1.5×, 1.75×, 2×, etc.) applied to the determinedfastener diameter. Such safety factors may be incorporated in order toincrease confidence that the attachment of the driving member to thepulley (via the compressive arrangement) will not fail during expecteduse of the pulley arrangement. It should be understood that althoughEquations (1)-(10) are described with reference to the compressivearrangement 300, these equations are not necessarily solely applicableto the compressive arrangement 300, and may be modified to determinedesired parameters of other attachment arrangements described herein.

In another exemplary variation, as shown in FIGS. 4A-4D, a compressivearrangement 400 for coupling a driving member to a pulley may include apulley 410, a driving member 420 with overlapping first and second ends422 and 424, respectively, and at least two opposing surfaces secured byat least one fastener 434 and nut 436 for clamping the overlapping endsof the driving member 420 to the pulley 410. As shown best in FIG. 4C,the opposing surfaces in the compressive arrangement 400 may include afirst washer 430 and a second washer 432 arranged on opposing sides ofthe pulley 410 and driving member ends 422 and 424. At least one of thewashers 430 and 432 may be a wave spring washer or the like, whichimparts a spring pressure when compressed in the compressivearrangement, so as to increase the likelihood that the compressivearrangement provides a positive compressive force at the attachmentlocation throughout the life of the pulley arrangement.

Generally, the fastener 434 (e.g., a threaded member such as a bolt orscrew) may pass through the first washer 430, the pulley 410, throughthe first and second ends 422 of the driving member 420, through thesecond washer 432, and through the nut 436. In some variations, thediameter of the fastener may be less than or equal to about half thewidth of the driving member 420. The nut 436, which is threadinglyengaged with the fastener 434, may be tightened to clamp and secure thepulley 410 and driving member ends together between the first washer 430and the second washer 432. The nut 436 may be a locknut or jam nut withthreadlocker, etc. in order to help secure the nut's location on thefastener 434 and maintain compressive force.

In some variations, as shown in FIG. 4B, the pulley 410 may include arecess to receive the head of the fastener (or alternatively, the nut436). Additionally or alternatively, as shown in FIG. 4D, the pulley 410may define a flat surface 412 against which the head of the fastener 434may abut such that the fastener does not rotate (e.g., while or afterthe compressive arrangement is tightened). During assembly, the washer430 may be inserted through a slot 414 in the pulley 410 to bepositioned in the path of the fastener 434.

In another exemplary variation, as shown in FIGS. 5A and 5B, acompressive arrangement 500 for coupling a driving member to a pulleymay include a pulley 510, a driving member 520 with overlapping firstand second ends 522 and 524, respectively, and at least two opposingsurfaces secured by one or more fasteners 534 and nuts 536 for clampingthe overlapping ends of the driving member 520 to the pulley 510. Asshown best in FIG. 5B, the opposing surfaces in the compressivearrangement 500 may include a washer 530 and a clamp 532 arranged onopposing sides of the pulley 510 and driving member ends 522 and 524.The clamp 532 may, for example, be similar to the clamp 330 describedabove with reference to FIGS. 3A and 3B.

Generally, the fasteners 534 may pass through the clamp 532, through thesecond and first ends 524 and 522, respectively, through the pulley 510,through the washer 530, and through the nut 536. In some variations, thediameter of a fastener 534 may be less than or equal to about half thewidth of the driving member 520. In some variations, the fasteners 534may be threaded (e.g., bolt or screw) and threadingly engage with holesin the pulley 510 and/or the nuts 536. In other variations, one or moreof the fasteners 534 may be press-fit into the pulley 510 to therebysecure the driving member 520 against the pulley 510.

As shown in FIG. 5A, the compressive arrangement 500 may be secured withmore fasteners having smaller diameters instead of fewer fastenershaving larger diameters. For example, the compressive arrangement 500 isdepicted as including five fasteners passing through a set of respectivefive holes in the clamp 534 and driving member ends 522 and 544. Morenumerous smaller holes, instead of fewer larger holes, may reduce stressconcentration around the holes that are more prone to failure (e.g., inthe event the shear strength of the attachment joint is overcome by thedriving forces of the pulley arrangement).

In another exemplary variation, as shown in FIGS. 6A-6D, a compressivearrangement 600 for coupling a driving member to a pulley may include apulley 610 having at least one projection 616, and a driving member 620with first and second ends 622 and 624 where at least one of the firstand second ends 622 and 624 wraps at least partially around a projection616 on the pulley 610. In the variation shown in FIG. 6C, each of thedriving member ends 622 and 624 may wrap around a respective projection616. The compressive arrangement 600 may further include at least twoopposing surfaces secured by at least one fastener 634 and nut 636 forclamping the driving member ends 622 and 624 onto the projections 616 ofthe pulley 610. As shown best in FIG. 6C, the opposing surfaces in thecompressive arrangement 600 may include a first clamp 640 disposed on afirst side (e.g., inner side) of the projections 616 and a second clamp642 disposed on a second side (e.g., outer side) of the projections 616.The clamps 640 and 642 may, for example, be similar to the clamp 330described above with reference to FIGS. 3A and 3B. The first clamp 640may be configured to compress parts of the driving member ends 622 and624 against the first side of the projections 616. The second clamp 642may be configured to compress parts of the driving member ends 622 and624 against the second side of the projections 616. Generally thefastener 634 may pass through the clamps 640 and 642 and nut 636 tocompress and secure the driving member ends around the projections 616of the pulley.

Additionally or alternatively, the opposing surfaces in the compressivearrangement 600 may include a first washer 630 and/or a second washer632. At least one of the washers 630 and 632 may be a wave spring washeror the like, which imparts a spring pressure when compressed in thecompressive arrangement, so as to increase the likelihood that thecompressive arrangement provides a positive compressive force at theattachment location throughout the life of the pulley arrangement.

Additionally or alternatively, the opposing surfaces clamping thedriving member ends 622 and 624 onto the projections 616 of the pulley610 may be on the fastener 634 itself. For example, the head of thefastener 634 may be shaped (e.g., machined) to match the curvature ofthe pulley 610, and be large enough to provide enough compressive forceon the driving member ends 622 and 624.

In some variations, similar to that described above with reference toFIG. 4B, the pulley 610 may include a recess to receive the head of thefastener (or alternatively, the nut 636). Additionally or alternatively,as shown in FIG. 6D, the pulley 610 may define a flat surface 612against which the head of the fastener 634 may abut such that thefastener does not rotate (e.g., while or after the compressivearrangement is tightened). During assembly, the washer 630 and/or clamp640 may be inserted through a slot 614 in the pulley 610 to bepositioned in the path of the fastener 634.

In another exemplary variation, as shown in FIG. 7, a compressivearrangement 700 is similar to compressive arrangement 600, except asdescribed below. The compressive arrangement 700 for coupling a drivingmember to a pulley may include a pulley 710 having at least oneprojection 716, and a driving member 720 with first and second ends 722and 724 where at least one of the first and second ends 722 and 724wraps at least partially around a projection 716 on the pulley 710. Inthe variation shown in FIG. 7, each of the driving member ends 722 and724 may wrap around a respective projection 716. The compressivearrangement 700 may further include a wedge 750 configured to compressthe driving member ends 722 against the projections 716. For example,the wedge 750 may be generally prismatic with tapered edges such thatthe wedge narrows in width along a radial direction. Alternatively, thewedge 750 may be conical or frustoconical, etc. The wedge may be made ofa high-friction material such as rubber or other suitable material. Afastener 734, secured by nut 736, may pass through a lumen of the wedge750 between the projections 716 such that as the fastener is tightened,the wedge 750 is urged radially and its increasing width at the pointsof contact with the driving member ends 722 and 724 causes the wedge 750to further compress the driving member ends 722 and 724 against theprojections 716 in the pulley.

The compressive arrangement 700 may further include at least one clamp740 disposed on an inner side of the projections 716 to help secure theends of the driving member to the pulley. The claim 740 may, forexample, be similar to the clamp 330 described above with reference toFIGS. 3A and 3B. Additionally or alternatively, the compressivearrangement 700 may include a first washer 730 and/or a second washer732. At least one of the washers 730 and 732 may be a wave spring washeror the like, which imparts a spring pressure when compressed in thecompressive arrangement, so as to increase the likelihood that thecompressive arrangement provides a positive compressive force at theattachment location throughout the life of the pulley arrangement.

In another exemplary variation, as shown in FIG. 8, a compressivearrangement 800 is similar to compressive arrangement 700, except asdescribed below. For example, the compressive arrangement 800 mayinclude a pulley 810 having at least one projection 816, and a drivingmember 820 with first and second ends 822 and 824, where at least one ofthe first and second ends wraps at least partially around a projectionon the pulley 810. The compressive arrangement 800 may further include awedge 850 such as that similar to wedge 750 described above withreference to FIG. 7. A threaded fastener 834, secured at one end with anut 836, may pass through a lumen of the wedge 850 and into a threadedhole of the pulley 810. As the fastener is tightened (e.g., nut 936 andwasher 832 are advanced against the wedge 850), the wedge 850 is urgedradially and its increasing width at the points of contact with thedriving member ends 822 and 824 causes the wedge 850 to further compressthe driving member ends 822 and 824 against the projections in thepulley 810. Another exemplary variation of a compressive arrangement 900is shown in FIG. 9. Compressive arrangement 900 is similar tocompressive arrangement 800, with elements numbered similar to those incompressive arrangement 800, except that the ends 922 and 924 of thedriving member wrap less around the projections 916 compared to ends 822and 824 of the driving member as shown in FIG. 8.

In another exemplary variation, as shown in FIG. 10A, a compressivearrangement 1000 may include a block 1010 (e.g., part of a pulley or acomponent coupled to a pulley) having one or more deformable pins 1034,a driving member 1020, and a clamp 1030. The pins 1034 may, for example,be machined out of the block 1010, and/or may be pins that are insertedinto respective holes in the block 1010 (e.g., via press-fit, etc.). Thepins may be received through holes 1022 in the driving member 1020 andholes 1032 in the clamp 1030 in the arrangement of FIG. 10B. As shown inFIG. 10B, the block 1010 and clamp 1030 may have mateable surfaces thatsandwich and compress the driving member on opposite sides of thedriving member.

As shown in FIG. 10C, a compressive force F may be applied to the blockand clamp assembly, so as to deform at least one of the pins 1034 into arivet or rivet-like shape that secures the driving member 1020 againstthe block 1010. For example, the compressive force F may be applied viaa clamp with one or more recesses, each recess receiving a respectivedistal end of a pin 1034 such that the recess molds or otherwise formsthe distal end of the pin 1034 into a rivet or rivet-like shape. Thecompressive force F may be applied to multiple (two or more, or all)pins 1034 simultaneously, or may be applied to each pin sequentially.

Furthermore, although the block 1010 and clamp 1032 are depicted in FIG.10A as having flat mateable surfaces, it should be understood that inother variations, they may have angled surfaces, curved surfaces (e.g.,arcuate with the same radius of curvature), or other suitable matingsurfaces. Particular dimensions, number, materials, etc. of pins on theblock may, in some variations, be selected based on an analysis ofparameters such as those utilized in Equations 1-10 as described above.

In some exemplary variations, the block 1010 and pins 1034 may made ofstainless steel (e.g., 304SST) or carbon steel, with or withoutadditional alloying elements (e.g., high strength low allow steel, whichmay include, for example, additional alloying elements such asmanganese, copper, titanium, vanadium, niobium, etc. to the carbon orany suitable material. The clamp may be made of annealed steel (e.g.,AISI 1010) or other suitable material that may be relatively soft (e.g.,to provide sufficient contact for improving friction). As shown in FIG.10A, the block 1010 may include five pins, each with a diameter of about1 mm, and may be arranged in a bilaterally symmetrical pattern such aswith four pins at four corners of a rectangle measuring about 4 mm×about3 mm and a fifth pin in the center of the rectangle. The formingoperation on the pins to deform the pins into rivets or rivet-likeshapes may be formed one at a time under a compressive force of about1500 N. In these variations, each forming operation may achieve, forexample, around 300N of clamping force to secure the driving member 1032to the block 1010.

Brazed Attachment

In some variations, a terminating end of a driving member may beattached to a pulley in the pulley arrangement via at least brazing. Thedriving member may include multiple layers of a metal material that arecoupled via brazing with a braze alloy filler material, and the drivingmember may further be coupled to a pulley or other component via brazingwith the same or different braze alloy filler material. The resultingbrazed joint may be as strong as or stronger than the strength of thefull cross-section of all metal strips.

For example, as shown in FIG. 11, a multi-layer driving member 1120(e.g., similar to that described above with reference to FIGS. 2A and2B) may be brazed to a metal block 1110. The metal block 1110 may beportion of a pulley or a component coupled to a pulley. The multi-layerdriving member may be brazed to an arcuate segment of the block sweepingan angle A, where angle A may be, for example, between about 10 degreesand 25 degrees, or between about 15 degrees and about 20 degrees. Themulti-layer driving member 1120 may include at least one metal beltlayers 1122 and at least one filler layer 1124. The metal belt layers1122 may include stainless steel or other suitable material. The fillerlayers 1124 may include a suitable braze alloy such as aluminum-silicon,copper or copper alloy, nickel alloy, etc. Although FIG. 11 depicts adriving member 1120 with two metal layers and two filler layers 1124, itshould be understood that any suitable number of metal belt layersand/or filler layers may be included.

In some exemplary variations, the block 1010 is an arcuate segment madeof stainless steel (e.g., 304SST) or carbon steel, with or withoutadditional alloying elements. The multi-layer driving member may includemultiple metal strips (e.g., 301-HY stainless steel) that are brazed toone another with a filler material. Additionally, the multi-layerdriving member may be brazed along the arc length of the block 1010 thatsweeps about 17.5 degrees. In one example, the driving member mayinclude up to about five layers of metal belt material each with athickness of about 0.13 mm and a width of about 6 mm. As anotherexample, the driving member may include up to about twelve layers ofmetal belt material each with a thickness of about 0.05 mmm and a widthof about 6 mm. These examples may result in a brazed joint having ashear strength of about 6800 N.

Tensioning Mechanisms

Described below are variations of tensioning mechanisms in pulleyarrangements that enable tensioning of driving members attached to oneor more pulleys. Generally, appropriately tensioned driving members helpfacilitate the rotational motion within a pulley arrangement (e.g.,within a pitch assembly such as pitch assembly 120 described above withreference to FIGS. 1C and 1D).

In some variations, the one or more driving members may be tensioned toa predetermined tension level at least during manufacturing, assembly,and/or calibration of the pitch assembly. Additionally or alternatively,the one or more driving members may be monitored and re-tensioned duringand over the course of use of the robotic arm. For example, throughoutoperation of a pulley arrangement, fatigue loads applied to the pulleyarrangement over an extended period of time may cause the one or moredriving members to slacken and lose their tension, thereby resulting inpoorer performance in the pulley arrangement (e.g., less positionalaccuracy, slower actuating response times, etc.). Thus, periodic orintermittent tensioning of the one or more driving members may bedesired in order to maintain performance. Additionally or alternatively,at least a portion of the pulley assembly may be swappable to bereplaced with appropriately-tensioned pulley assembly parts, such aspart of regular maintenance.

Accordingly, in some variations, a pulley arrangement (such as oneincluded in the pitch assembly 120 as shown in FIGS. 1C and 1D in arobotic arm) may further include a tensioning mechanism. For example,the tensioning mechanism can include at least one tensioner pulleylocated in plane with the first and second pulleys 162 and 164 andcorresponding one or more bands, and at least one tensioner pulleylocated in plane with the third and fourth pulleys 166 and 168 andcorresponding one or more bands. The in-plane locations of thetensioning pulleys may be adjusted and set (e.g., with fasteners) inorder to calibrate the tension of the bands. However, the pitch assembly120 may include a turnbuckle, or any suitable tensioning assembly. Otherexemplary variations of tensioning mechanisms, such as those describedbelow, may be incorporated in the pulley arrangement.

Split Pulleys

In some variations, as shown in FIG. 12A, a pulley arrangement 1200 mayinclude an adjusting pulley 1210 and an idler pulley 1230 that areconnected via a first driving member 1220 and a second driving member1220′. A first end 1222 of a first driving member 1220 may couple to andwrap at least partially around the adjusting pulley 1210, and a secondend 1224 of the first driving member 1220 may couple to and wrap atleast partially around the idler pulley 1230. Similarly, a first end1222′ of a second driving member 1220′ may couple to and wrap at leastpartially around the adjusting pulley 1210, and a second end 1224′ ofthe second driving member 1220′ may couple to and wrap at leastpartially around the idler pulley 1230. Alternatively, the adjustingpulley 1210 and the idler pulley 1230 may be connected via a singledriving member 1220, with a first end 1222 of the driving member 1220coupled to and wrapping at least partially around the adjusting pulley1210, a body portion of the driving member 1220 wrapping around theidler pulley 1230, and a second end 1224 of the driving member 1220coupled to and wrapping at least partially around the adjusting pulley1210. Any suitable attachment mechanism or arrangement, including any ofthe driving member attachment variations described herein, may be usedto couple an end of one or both driving members to the adjusting pulleyand/or idler pulley. The pulley arrangements with adjusting pulleysdescribed below may, for example, be used to adjust tension in thedriving member in those variations in which the idler pulley may be afixed distance from the base pulley portion (though in some variationsthe idler pulley position may be adjustable in distance from the basepulley portion, such as to further adjust tension in the driving memberor members).

In some variations, a pulley arrangement may include an adjusting pulleyfor adjusting tension in the pulley arrangement, the adjusting pulleyincluding a base pulley portion rotatable within a driving plane, and anadjustable pulley portion coupled to the base pulley portion. Theadjustable pulley portion may be rotatable relative to the base pulleyportion within the driving plane. The pulley arrangement may furtherinclude a driving member comprising a first end coupled to theadjustable pulley portion, wherein at least a portion of the drivingmember is wrapped at least partially around the adjustable pulleyportion. Examples of these variations are shown in FIGS. 12A-12C andFIGS. 14A-14B.

As shown in FIGS. 12A-12C, a pulley arrangement may include a basepulley portion 1212, an adjustable pulley portion 1214 rotatablerelative to the base pulley portion 1212, and at least one drivingmember 1220 having a first end 1222 coupled to and wrapping at leastpartially around the adjustable pulley portion 1214. Another drivingmember end 1222′ (of the same driving member 1220 or another drivingmember 1220′) may be coupled to the base pulley portion 1212 and wrap atleast partially around the base pulley portion 1212. The base pulleyportion and the adjustable pulley portion may be generally circular orarcuate. For example, the base pulley portion and/or the adjustablepulley portion may be ring-like or partial ring-like as shown in FIGS.12B and 12C. Alternatively, the base pulley portion and/or theadjustable pulley portion may be in the shape of a disc or partial discwith an arcuate edge.

As shown in FIG. 12A, the base pulley portion 1212 may include amounting region 1212 a and a driving region 1212 b. The mounting region1212 a may be configured to mount the base pulley portion 1212 to asurrounding structure (e.g., an arm segment such as a pitch link in arobotic arm), such as with fasteners. The driving region 1212 b mayinclude an arcuate surface configured to engage with the driving member1220. For example, the driving member 1220 may wrap at least partiallyaround the arcuate surface of the driving region 1212 b. In somevariations, the driving region 1212 b may be a surface that is at leastabout the width of the driving member 1220.

Like the base pulley portion 1212, the adjustable pulley portion 1214may include a mounting region 1214 a and a driving region 1214 b. Themounting region 1214 a may be configured to couple the adjustable pulleyportion 1214 to the base pulley portion 1212. For example, as shown inFIG. 12B, one or more fasteners 1213 (e.g., screws, bolts, etc.) maypass through openings 1215 and into threaded holes (not shown) in thebase pulley portion 1212, in order to axially constrain the adjustablepulley portion 1214 relative to the base pulley portion 1212. Thedriving region 1214 b may include an arcuate surface configured toengage with the driving member 1220. For example, the driving member1220 may wrap at least partially around the arcuate surface of thedriving region 1214 b. In some variations, the driving region 1214 b maybe a surface that is at least about the width of the driving member1220. Furthermore, as shown for example in FIG. 12C, one end of thedriving member 1220 may be coupled (e.g., with any of the attachmentarrangements described herein, or in any suitable manner) to the drivingregion 1214 b at point A of the adjustable pulley portion 1214.

The driving region 1214 b of the adjustable pulley and the drivingregion 1212 b of the base pulley portion may, in combination,approximate at least part of a circle. For example, the driving region1214 b and the driving region 1212 b may be nearly semi-circular. Asanother example, the driving region 1212 b may sweep a major arc whilethe driving region 1214 b sweeps a minor arc, or vice versa. As yetanother example, both the driving region 1214 b and the driving region1212 b may sweep a minor arc. The adjustable pulley portion 1214 and thedriving region 1212 b of the base pulley portion may be generallycoaxial and have approximately the same radius of curvature, such that adriving member 1220 and/or a driving member 1220′ may rotate with thepulley arrangement at a consistent rate of travel.

The adjustable pulley portion 1214 may be configured to rotate relativeto the base pulley portion 1212. As described above, one end of thedriving member 1220 may be coupled to and wrapped at least partiallyaround the adjustable pulley portion 1214, and another end of thedriving member 1220 may be coupled to a ground location (e.g., idlerpulley 1230 as shown in FIG. 12A or point B on the base pulley portion1212 as shown in FIG. 12C). In such an arrangement, the adjustablepulley portion 1214 may be radially constrained to rotate relative tothe base pulley portion via a kinematic constraint between the pulleyportions and the tension of the belt.

Furthermore, rotation of the adjustable pulley portion 1214 in aparticular direction relative to the base pulley portion 1212 maytension the driving member 1220. In some variations, pulley arrangementmay include a movable element engaged with the adjustable pulleyportion, where the movable element may be adjustable to thereby rotatethe adjustable pulley portion 1214 relative to the base pulley portion1212. For example, the movable element may include a threaded member1216 (e.g., carriage bolt or other suitable fastener). One end of thethreaded member 1216 may be coupled to the base pulley portion 1212, andanother end of the threaded member 1216 may be in contact with theadjustable pulley portion 1214. Advancement and/or retraction of thethreaded member 1216 may cause displacement of the adjustable pulleyportion 1214.

FIGS. 13A-13C depict various exemplary rotational positions of theadjustable pulley portion 1214 corresponding to different levels oftension in the driving member 1220. In FIG. 13A, the adjustable pulleyportion 1214 is in a rotational position corresponding to a relativelylow amount of tension in the driving member. The threaded member 1216 isin a retracted state. In this rotational position, the fasteners 1213that axially couple the adjustable pulley portion 1214 to the basepulley portion 1212 are generally located at a first end (e.g., rightend, as depicted in FIG. 13A) of the slot openings 1215.

In FIG. 13B, the adjustable pulley portion 1214 is in a rotationalposition corresponding to a moderate amount of tension in the drivingmember. The threaded member 1216 is advanced upwards (in the orientationshown in FIG. 13B) by a moderate distance to thereby rotationallydisplace the adjustable pulley portion 1214 in a clockwise direction. Inthis adjusted rotational position, the adjustable pulley portion 1214causes the end of the driving member 1220 attached at “A” to be closerto the end of the driving member attached at “B,” which increasestension in the driving member. In this rotational position, thefasteners 1213 are generally located in the middle of the slot openings1215.

In FIG. 13C, the adjustable pulley portion 1214 is in a rotationalposition corresponding to a relatively high amount of tension in thedriving member. The threaded member 1216 is advanced further than inFIG. 13B to thereby further displace the adjustable pulley portion 1214in a clockwise direction. In this adjusted rotational position, theadjustable pulley portion 1214 causes the end of the driving memberattached at “A” to be even closer to (e.g., adjacent to) the end of thedriving member attached at “B,” which further increases tension in thedriving member compared to the arrangement of FIG. 13B. In thisrotational position, the fasteners 1213 are generally located at asecond end of the slot openings 121.

The three levels of tension are depicted in FIGS. 13A-13C asillustrative examples. It should be understood that the possible rangeof selectable tension in the driving member may be continuous andinclude levels of tension between those depicted in FIGS. 13A-13C.Additionally, in some variations, levels of tension may be attainablebeyond the low and high levels of tension depicted in FIGS. 13A and 13C.For example, the adjustable pulley portion 1214 may be positioned at amore counter-clockwise position than in FIG. 13A, which corresponds toan even lower level of tension in the driving member. As anotherexample, such as if the driving regions 1212 b and 1214 b (of the basepulley portion and adjustable pulley portion, respectively) may beoverlapped, the adjustable pulley portion 1214 may be positioned at amore clockwise position than FIG. 13C, which enables the driving memberends at “A” and “B” to overlap and result in an even higher level oftension in the driving member compared to FIG. 13C. Furthermore, in somevariations, the possible range of selectable tension may be discrete(e.g., via detents in the openings 1215, etc.).

As shown in FIGS. 13A-13C, in some variations, the threaded member 1216may include a hemi-spherical head configured to contact the adjustablepulley portion at a tangential point as the rotational position of theadjustable pulley portion 1214. By contacting the adjustable pulleyportion 1214 only at a single point as the rotational position of theadjustable pulley portion varies, the hemi-spherical head of thethreaded member 1216 may help ensure proper kinematic coupling betweenthe base pulley portion, the adjustment pulley portion, and the threadedmember 1216. In some variations, the hemi-spherical head of the threadedmember 1216 may have a single radius of curvature such that the rate oflinear travel of the threaded member 1216 corresponds to a consistentrate of rotational travel of the adjustable pulley portion, andtherefore results in a consistent amount of tensioning per unit oftravel of the threaded member 1216. In other words, the ratio between aunit of linear travel of the threaded member 1216 and a unit ofrotational travel of the adjustable pulley portion may be generallyconstant while the head of the threaded member 1216 and the adjustablepulley portion are in contact.

Furthermore, in some variations, as shown in FIGS. 13A-13C, the threadedmember 1216 may include one or more features that may be engaged toadvance and/or retract the threaded member 1216 relative to the basepulley portion. For example, the threaded member 1216 may include alongits length one or more flat surfaces that may be grasped with a clamp,wrench, or other suitable tool from a lateral or radial approachrelative to the length of the threaded member (e.g., since the head ofthe threaded member 1216 may be at least partially obstructed by theadjustable pulley portion). Such a tool may be used to grasp and turnthe threaded member 1216 to advance and/or retract the threaded member1216. Alternatively, an underside of the head of the threaded member, orother suitable portion of the threaded member, may be engaged to advanceand/or retract the threaded member and rotate the adjustable pulleyportion 1214.

The adjustable pulley portion may be lockable in a selected rotationalposition relative to the base pulley portion, thereby setting a selectedtension level in the driving member. For example, once the adjustablepulley portion's rotational position is selected, the fasteners 1213 maybe tightened in their locations in the slot openings 1215 to therebylock the adjustable pulley portion in the selected rotational position(and lock the selected tension level in the driving member). Thus, bymoving the adjustable pulley portion and locking its rotationalposition, the tension of the driving member maybe adjusted and lockedduring assembly of the pulley arrangement (e.g., as part of themanufacturing process), during a calibration procedure, and/or duringmaintenance, etc.

Another variation of a pulley arrangement 1400 is shown in FIGS. 14A and14B. The pulley arrangement 1400 is similar to pulley arrangement 1200shown in FIG. 12A except as described below, with similar numbering ofelements. For example, the pulley arrangement 1400 may include anadjusting pulley 1410 and an idler pulley 1430 that are connected via atleast one driving member 1420. Any suitable attachment mechanism orarrangement, including any of the driving member attachment variationsdescribed herein, may be used to couple an end of one or both drivingmembers to the adjusting pulley and/or idler pulley. The pulleyarrangements with adjusting pulleys described below may, for example, beused to adjust tension in the driving member in those variations inwhich the idler pulley may be a fixed distance from the base pulleyportion (though in some variations the idler pulley position may beadjustable in distance from the base pulley portion, such as to furtheradjust tension in the driving member or members).

As shown in FIG. 16D, the idler pulley 1630 may include a base 1632 anda flange 1634 axially aligned with and coupled to the base 1632. Thebase 1632 may include a driving region around which at least part of thedriving member 1620 and/or the driving member 1620′ may be wrapped. Endsof the driving members 1620 and/or 1620′ may be coupled to the base 1632via anchor blocks 1622 engaged with base 1632, or in any suitable manner(e.g., attachment methods described herein). The flange 1634 may, forexample, provide a wall that guides the driving members along thedriving region of the base 1632 and helps prevent the driving membersfrom slipping out of plane with the pulley arrangement.

The pulley arrangement 1400 may include an adjusting pulley 1410 asshown in FIG. 14B. The adjusting pulley 1410 may include a base pulleyportion 1412, and an adjustable pulley portion 1414 rotatable relativeto the base pulley portion 1412. At least one driving member (notpictured) may have a first end coupled to (e.g., at location “A”) andwrap at least partially around the adjustable pulley portion 1414.Another driving member end may be coupled to (e.g., at location “B”) andwrap at least partially around the base pulley portion 1412.

As shown in FIG. 14B, the adjustable pulley portion 1414 may include aplurality of openings 1415 by which fasteners may axially couple theadjustable pulley portion 1414 to the base pulley portion 1412. Theplurality of openings 1415 may selectively align with one or moreopenings in the base pulley portion 1412. Each of the openings 1415,when aligned with an opening in the base pulley portion 1412, maycorrespond to a respective rotational position of the adjustable pulleyportion 1414 relative to the base pulley portion 1412, and thus maycorrespond to a respective level of tension in the driving member.Similar to that in the pulley arrangement 1200 described above, theselected rotational position of the adjustable pulley portion 1414 maybe locked by tightening a fastener or pin (not shown) in the alignedholes to thereby lock the tension of the driving member. Additionally oralternatively, the base pulley portion 1412 may include a plurality ofopenings that selectively align with one or more openings in theadjustable pulley portion 1414 so as to provide for multiple potentialrotational positions of the adjustable pulley portion 1414 and tensionlevels in the driving member. In some variations, the adjustable pulleyportion 1414 and/or the base pulley portion 1412 may include openingsarranged akin to a Vernier scale to provide many options for discretelevels of tension in the driving member.

Angled Surface Pulleys

Another variation of a pulley arrangement 1600 is shown in FIGS. 16A and16B. The pulley arrangement 1600 is similar to pulley arrangement 1200shown in FIG. 12A except as described below, with similar numbering ofelements. For example, the pulley arrangement 1600 may include anadjusting pulley 1610 and an idler pulley 1630 that are connected via atleast one driving member 1620 (e.g., driving member 1620 and seconddriving member 1620′). Any suitable attachment mechanism or arrangement,including any of the driving member attachment variations describedherein, may be used to couple an end of one or both driving members tothe adjusting pulley and/or idler pulley. The pulley arrangements withadjusting pulleys described below may, for example, be used to adjusttension in the driving member in those variations in which the idlerpulley may be a fixed distance from the base pulley portion (though insome variations the idler pulley position may be adjustable in distancefrom the base pulley portion, such as to further adjust tension in thedriving member or members).

As shown in the exploded view of FIG. 16B and the assembled views ofFIGS. 16E and 16F, the adjusting pulley 1610 may include a base pulleyportion 1640 rotatable around an axis, an adjustable pulley portion 1650coupled to the base pulley portion, and at least one sliding block(e.g., sliding blocks 1660 a and 1660 b) engaged with the adjustablepulley portion 1650. As shown in FIG. 16F, the adjustable pulley portion1650 may be movable in a first direction (e.g., direction “Z”) parallelto the axis of rotation of the base pulley portion 1640. The at leastone sliding block may be configured to move in a second direction (e.g.,direction “R”) different from the first direction, in response tocompression of the adjustable pulley portion 1650 against the basepulley portion 1640. In some variations, the first and second directionsmay be generally orthogonal to each other.

The base pulley portion 1640 may be configured to fixedly mount, forexample, to a distal end of a pitch link (e.g., pitch link 1512 shown inFIG. 15A) or other portion of a robotic arm. As shown in FIG. 16I, thebase pulley portion 1640 may have a mounting face configured to matewith the adjustable pulley portion 1650 and the sliding blocks 1660 aand 1660 b. The mounting face may, for example, include at least oneridge or other guide 1642 configured to engage the sliding blocks 1660 aand 1660 b. The base pulley portion 1640 may be a generally circularplate or disc as shown in FIG. 161, but alternatively may have anysuitable shape with one or more mounting features. In some variations,cutouts in the material of the base pulley portion 1640 may help reduceweight of the overall adjusting pulley assembly. The base pulley portionmay be fitted with one or more pins 1646 configured to engage the holes1656 in adjustable pulley portion 1650 such that the adjustable pulleyportion 1650 rotates in 1:1 correspondence with the base pulley portion1640. The pins 1646 may transfer torque from the base pulley portion1640 to the adjustable pulley portion 1650, while allowing theadjustable pulley portion 1650 to move axially closer to and/or fartherfrom the base pulley portion 1640.

As shown in FIG. 16H, the adjustable pulley portion 1650 may begenerally circular (e.g., ring or plate) and may have a driving region1652 on an outer surface of the adjustable pulley portion 1650, aroundwhich one or more driven members are wrapped. The adjustable pulleyportion 1650 may mate and couple with the mounting features of the basepulley portion 1640, such as with fasteners 1650 (e.g., screws) thatpass through the holes 1658 of the adjustable pulley portion and engagethreaded holes 1644 of the base pulley portion 1640. Additionally, theadjustable pulley portion 1650 may have an arcuate gap betweenspaced-apart surfaces 1654. Surfaces 1654 may be sloped (e.g., helicalsurfaces) in complementary fashion with sloped surfaces 1664 (e.g.,helical surfaces) of sliding blocks 1660 a and 1660 b.

As shown in FIGS. 16E and 16F, the sliding blocks 1660 a and 1660 b maybe disposed in the arcuate gap between spaced-apart surfaces 1654.Grooves 1666 of the sliding blocks may engage the outwardly-projectingguide 1642 on the base pulley portion (though alternatively, the guide1642 may be a groove and the sliding blocks may include anoutwardly-projecting guide). With reference to FIG. 16G, an end of adriving member may attached to a driving region 1662 on an outer surfaceof the sliding block 1660 b. Similarly, an end of the same or anotherdriving member may be attached to a driving region on an outer surfaceof the sliding block 1660 a. The driving regions of the adjustablepulley portion 1650 and the sliding blocks 1660 a and 1660 b may bealigned so as to facilitate a smooth transition for a driving member towrap around the driving regions.

The adjusting pulley 1610 may facilitate bilateral tensioning of thedrive members 1620 and 1620. Generally, as shown in FIG. 16F, an inputforce may apply compression of the adjustable pulley portion 1650against the base pulley portion 1640 and move the adjustable pulleyportion 1650 in the direction “Z” (thereby bringing the adjustablepulley portion 1650 and the base pulley portion 1640 in closerapproximation to each other). The input force may be applied bytightening the fasteners 1670 to tightening the adjustable pulleyportion 1650 against the base pulley portion 1640. This axially-directedinput force is translated, by sloped mating surfaces 1654 (on theadjustable pulley portion) and 1664 (on the sliding blocks), to move thesliding blocks circumferentially together. In other words, in responseto this input force in the “Z” direction, the first and second slidingblocks 1660 a and 1660 b are configured to move circumferentially orarcuately toward each other in the “R” directions, thereby bringing thedriving member ends (attached to the sliding blocks) together andapplying tension to the driving member or members. If the helicalsurfaces 1664 on the sliding blocks are similar in slope, etc. (e.g.,the sliding blocks 1660 a and 1660 b are mirror images of one another),then the sliding blocks 1660 a and 1660 b may move circumferentially orarcuately toward each other at about equal rates. If the helicalsurfaces 1664 on the sliding blocks are not similar in slope, then thesliding blocks 1660 a and 1660 b may move circumferentially or arcuatelytoward each other at different rates.

When a desired level of tensioning in the driving member or members isachieved with a particular axial position of the adjustable pulleyportion 1650 relative to the base pulley portion 1640, one or more ofthe fasteners 1670 may be set to lock the tensioning level. For example,the axial position of the fasteners 1670 may be set with a locknut, jamnut with threadlocker, etc.

Therefore, a single input action of bringing the adjustable pulleyportion and the base pulley portion closer together results intightening the driving members, which may improve ease of setup andmaintenance throughout the lifetime of the pulley mechanism.Additionally, with symmetrical sliding blocks, equal tension may beapplied to both bands, which may improve load rating and lifetime of thepulley mechanism. Furthermore, within a single pulley arrangementincluding an adjustable pulley and an idler pulley, advantageously onlyone pulley may be required to provide adjustable termination of thebands.

Another variation of an adjusting pulley 1710 is shown in FIG. 17. Theadjusting pulley 1710 is similar to adjusting pulley 1610, except asdescribed below, with similar numbering of elements. In the adjustingpulley 1710, the adjustable pulley portion includes two members 1750 aand 1750 b. The first member 1750 a may be engaged with a first slidingblock 1760 a, and the second member 1750 b may be engaged with a secondsliding block 1760 b. Similar to the adjustable pulley portion 1650described above, the members 1750 a and 1750 b may be movable parallelto the axis around which the base pulley portion 1740 rotates. When thefirst member 1750 a moves in such an axial direction toward the basepulley portion 1740, interfacing sloped (e.g., helical) surfaces of thefirst member 1750 a and the first sliding block 1760 a may translateinto a circumferential or arcuate movement of the first sliding block1760 a toward the second sliding block 1760 b. Similarly, when thesecond member 1750 b moves in an axial direction toward the base pulleyportion 1740, interfacing sloped (e.g., helical) surfaces of the secondmember 1760 b and the second sliding block 1760 b may translate into acircumferential or arcuate movement of the second sliding block 1760 btoward the first sliding block 1760 a. Therefore, like the adjustingpulley 1610 described above, a single input action of bringing theadjustable pulley portion and the base pulley portion closer together inthe adjusting pulley 1710 results in tightening the driving members.

The members 1750 a and 1750 b may be moved independent of one another,which may enable independent tensioning of the driving member endscoupled to each member 1750 a and 1750 b. Furthermore, the members 1750a and 1750 b may be moved in tandem, which may enable simultaneoustensioning of the driving member ends coupled to the members 1750 a and1750 b.

When a desired level of tensioning in the driving member or members isachieved with a particular axial position of the adjustable pulleyportion relative to the base pulley portion 1740, one or more of thefasteners 1770 may be set to lock the tensioning level. For example, theaxial position of the fasteners 1770 may be set with a locknut, jam nutwith threadlocker, etc.

Another variation of an adjusting pulley 1810 is depicted in FIGS. 18Aand 18B. The adjusting pulley 1810 is similar to adjusting pulley 1810,except as described below, with similar numbering of elements. In theadjusting pulley 1810, the adjustable pulley portion includes twomembers 1850 a and 1850 b, each of which is disposed in a recess of thebase pulley portion 1840 such that the adjustable pulley portion and thebase pulley portion 1840 are in-plane with each other (instead ofgenerally adjacent to each other as in adjusting pulleys 1610 and 1710).The adjustable pulley portion members 1850 a and 1850 b may engage withfirst and second sliding blocks 1860 a and 1860 b, respectively. Asshown in FIG. 18B, the end of driving member 1820 is wrapped around thebase pulley portion, around a projection 1842 a, over the adjustablepulley portion member 1850 a, and is coupled to the first sliding block1860 a. Similarly, the end of driving member 1820′ (or alternatively, asecond end of driving member 1820) is wrapped around the base pulleyportion, around a projection 1842 b, over the adjustable pulley portionmember 1850 b, and is coupled to the second sliding block 1860 b. Thedriving member ends may be coupled to the sliding blocks 1860 a and 1860b using, for example, any of the attachment arrangements describedherein, or any suitable attachment arrangement.

Similar to the adjustable pulley portion described above with respect toFIG. 17, the members 1850 a and 1850 b may be movable parallel to theaxis around which the base pulley portion 1840 rotates. When the firstmember 1850 a moves in such an axial direction toward the base pulleyportion 1840, interfacing sloped (e.g., slanted, linearly slanted)surface of the first member 1850 a and the first sliding block 1860 amay translate into linear movement of the first sliding block 1860 a inthe recess away from the projection 1842 a, thereby tensioning the endof driving member 1820. Similarly, when the second member 1850 b movesin an axial direction toward the base pulley portion 1840, interfacingsloped (e.g., slanted, linearly slanted) surface of the second member1850 b and the second sliding block 1860 b may translate into linearmovement of the second sliding block 1860 b in the recess away from theprojection 1842 b, thereby tensioning the end of driving member 1820′.

The members 1850 a and 1850 b may be moved independent of one another,which may enable independent tensioning of the driving member endscoupled to each member 1850 a and 1850 b. Furthermore, the members 1850a and 1850 b may be moved in tandem, which may enable simultaneoustensioning of the driving member ends coupled to the members 1850 a and1850 b. In some variations, during a process of tensioning, the drivingmembers may be worked back and forth (by cyclically tensioning andslightly loosening the driving members) to distribute the tension acrossthe length of the driving members.

When a desired level of tensioning in the driving member or members isachieved with a particular axial position of the adjustable pulleyportion relative to the base pulley portion 1840, one or more of thefasteners 1870 may be set to lock the tensioning level. For example, theaxial position of the fasteners 1870 may be set with a locknut, jam nutwith threadlocker, etc.

The foregoing description, for purposes of explanation, used specificnomenclature to provide a thorough understanding of the invention.However, it will be apparent to one skilled in the art that specificdetails are not required in order to practice the invention. Thus, theforegoing descriptions of specific embodiments of the invention arepresented for purposes of illustration and description. They are notintended to be exhaustive or to limit the invention to the precise formsdisclosed; obviously, many modifications and variations are possible inview of the above teachings. The embodiments were chosen and describedin order to best explain the principles of the invention and itspractical applications, they thereby enable others skilled in the art tobest utilize the invention and various embodiments with variousmodifications as are suited to the particular use contemplated. It isintended that the following claims and their equivalents define thescope of the invention.

1. A pulley arrangement, comprising: a base pulley portion rotatablewithin a driving plane; an adjustable pulley portion coupled to the basepulley portion, wherein the adjustable pulley portion is rotatablerelative to the base pulley portion within the driving plane; and adriving member comprising a first end coupled to the adjustable pulleyportion, wherein at least a portion of the driving member is wrapped atleast partially around the adjustable pulley portion.
 2. The pulleyarrangement of claim 1, wherein the adjustable pulley portion islockable in a selected rotational position relative to the base pulleyportion, thereby setting a selected tension in the driving member. 3.The pulley arrangement of claim 1, wherein the adjustable pulley portionis coupled to the base pulley portion via at least one opening in atleast one of the adjustable pulley portion and the base pulley portion.4. The pulley arrangement of claim 3, further comprising a fastenerpassing through the at least one opening, wherein the fastener islockable in the at least one opening to thereby lock a rotationalposition of the adjustable pulley portion relative to the base pulleyportion.
 5. The pulley arrangement of claim 4, wherein the at least oneopening is a slot and wherein the fastener is lockable in a selectedlocation within the slot to thereby lock the rotational position of theadjustable pulley portion relative to the base pulley portion.
 6. Thepulley arrangement of claim 4, wherein the at least one opening is oneof a plurality of openings in at least one of the adjustable pulleyportion and the base pulley portion, each opening corresponding to arespective rotational position of the adjustable pulley portion relativeto the base pulley portion, and wherein the fastener is lockable in theat least one opening to thereby lock the rotational position of theadjustable pulley portion relative to the base pulley portion.
 7. Thepulley arrangement of claim 1, further comprising a movable elementengaged with the adjustable pulley portion and adjustable to therebyrotate the adjustable pulley portion relative to the base pulleyportion.
 8. The pulley arrangement of claim 7, wherein the movableelement comprises a threaded member.
 9. The pulley arrangement of claim8, wherein the threaded member comprises a hemi-spherical headcontacting the adjustable pulley portion.
 10. The pulley arrangement ofclaim 1, further comprising a second pulley, wherein the driving memberwraps at least partially around the idler pulley.
 11. The pulleyarrangement of claim 10, wherein the second pulley is a fixed distancefrom the base pulley portion.
 12. The pulley arrangement of claim 1,wherein the driving member comprises a second end coupled to the secondpulley.
 13. The pulley arrangement of claim 12, further comprising asecond driving member comprising a third end coupled to the base pulleyportion and a fourth end coupled to the second pulley.
 14. The pulleyarrangement of claim 1, wherein the adjustable pulley portion comprisesan arcuate member that is coaxial with the base pulley portion.
 15. Apulley arrangement, comprising: a base pulley portion rotatable aroundan axis; an adjustable pulley portion coupled to the base pulley portionand movable in a first direction parallel to the axis; and a firstsliding block engaged with the adjustable pulley portion; wherein thefirst sliding block is configured to move in a second directiondifferent from the first direction, in response to compression of theadjustable pulley portion against the base pulley portion.
 16. Thepulley arrangement of claim 15, further comprising a driving membercomprising a first end coupled to the first sliding block, wherein atleast a portion of the driving member is wrapped at least partiallyaround the first sliding block.
 17. The pulley arrangement of claim 16,wherein at least a portion of the driving member is wrapped at leastpartially around the adjustable pulley portion.
 18. The pulley mechanismof claim 15, wherein the adjustable pulley portion includes at least onesloped surface engaged with the first sliding block.
 19. The pulleymechanism of claim 18, wherein the sloped surface is a helical surface.20. The pulley mechanism of claim 15, wherein the first sliding blockincludes at least one sloped surface.
 21. The pulley mechanism of claim20, wherein the sloped surface is a helical surface.
 22. The pulleymechanism of claim 15, further comprising a second sliding block engagedwith the adjustable pulley portion, wherein the first and second slidingblocks are disposed in an arcuate gap in the adjustable pulley portionand engaged with the adjustable pulley portion, wherein the first andsecond sliding blocks are configured to move circumferentially towardeach other in response to compression of the adjustable pulley portionagainst the base pulley portion.
 23. The pulley mechanism of claim 22,wherein the first and second sliding blocks are configured to movecircumferentially toward each other at about equal rates in response tocompression of the adjustable pulley portion against the base pulleyportion.
 24. The pulley mechanism of claim 22, wherein the first andsecond sliding blocks are disposed in an arcuate gap defined at least inpart by the adjustable pulley portion.
 25. The pulley mechanism of claim22, further comprising a first driving member comprising a first endcoupled to the first sliding block and a second driving membercomprising a second end coupled to the second sliding block.
 26. Thepulley mechanism of claim 22, further comprising a driving membercomprising a first end coupled to the first sliding block and a secondend coupled to the second sliding block.
 27. The pulley mechanism ofclaim 22, wherein the adjustable pulley portion comprises a first memberengaged with the first sliding block and a second member engaged withthe second sliding block, wherein the first and second members aremovable in directions parallel to the axis.
 28. The pulley mechanism ofclaim 15, wherein an axial position of the adjustable pulley portionrelative to the base pulley portion is lockable.
 29. The pulleymechanism of claim 28, wherein the axial position is lockable via one ormore fasteners.
 30. The pulley mechanism of claim 15, wherein theadjustable pulley portion is adjacent the base pulley portion.
 31. Thepulley mechanism of claim 15, wherein the first sliding block isconfigured to move in an arcuate path in response to compression of theadjustable pulley portion against the base pulley portion.
 32. Thepulley mechanism of claim 15, wherein the first sliding block isconfigured to move in a linear path in response to compression of theadjustable pulley portion against the base pulley portion.
 33. Thepulley mechanism of claim 15, wherein the adjustable pulley portion isdisposed in a recess of the base pulley portion.
 34. The pulleyarrangement of claim 15, further comprising a second pulley, wherein atleast one driving member wraps at least partially around the secondpulley.